本文旨在研製三相三階層雙向功率轉換器。文中之系統採用T型三階層轉換器，減少了中性點箝位型轉換器的6個箝位二極體，可節省成本。本系統應用三相三階層弦式脈波寬調變及中性點電位平衡控制，有效降低市電側總電流諧波失真率。控制策略方面，則將直流側上臂及下臂電容電壓回授作電壓平衡及責任週期命令補償，以提高性能。

本系統採用32位元數位信號處理器TMS320F28335為系統之控制核心，控制策略皆由軟體程式完成。實驗結果顯示，當三相T型三階層功率轉換器直流側輸出功率為4.0kW時，市電側總電流諧波失真率為2.40%，效率為94.9%，直流側上臂及下臂電容電壓分別為191V及190V;而在相同的直流側輸出功率4.0kW下，三相T型二階層功率轉換器市電側電流總諧波失真率為3.26%，效率為93.06%，三階層的性能較佳。另者，當三相T型三階層換流器在功率由直流側饋至交流(市電)側，市電側消耗功率為4.3kW時，市電側總電流諧波失真率為3.82%，效率為94.8%，直流側上臂及下臂電容電壓分別為190V及191V，優於三相二階層換流器市電側總電流諧波失真率之實測值3.91% 及效率之實測值94.04%。實測結果驗證了本文系統架構與控制策略之可行性。

關鍵詞:三相三階層功率轉換器、電壓平衡控制、三階層弦式脈波寬調變

Abstract
This thesis is concerned with the development of bidirectional three-phase three-level power converters. T-type converter, which requires 6 less clamped diodes as compared with neutral-point-clamped converter, is chosen for cost reduction. The total harmonic distortion (THD) of current is reduced by using three-phase three-level sinusoidal pulse-width modulation as well as neutral-point voltage balancing control strategy. In addition, the voltages of the upper and lower capacitors are fed back for dc voltage balance control and duty cycle command compensation for performance improvement.
The 32-bits digital signal processor, TMS320F28335, is used as the control core. Control operations are mainly accomplished by the software program. The experimental results show that, under the output dc power of 4.0kW, the THD of current and efficiency of three-phase three-level T-type power converter are 2.40% and 94.9%, respectively, superior to the corresponding values of 3.26% and 93.06% of three-phase two-level power converter. Besides, the voltages of the upper and lower capacitors on the dc side are 191V and 190V, respectively, for three-phase three-level T-type inverter. Finally, when the three-phase three-level T-type inverter transfers 4.3kW of ac power from the dc side, the measuredTHD of current and efficiency are 3.82% and 94.8%, respectively, better than the corresponding values of 3.91% and 94.04% of three-phase two-level T-type inverter. The dc voltages of upper and lower capacitors are 191V and 190V, respectively, for three-phase three-level T-type inverter. The feasibility of the proposed system structure and control strategy is verified experimentally.
Keywords:three-phase three-level power converters, voltage balancing control, three-level sinusoidal pulse-width modulation.

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